<PRE><B>Question 962620</B>
I have to be at a certain place at a certain time and find that
 I shall be 20 minutes too late if I walk at 3km/hr
 10 minutes too early if I walk at 4km/hr.
 How far I have to walk?
:
The walking time difference between the two trips; 20 min + 10 min = 30 min
30 min = {{{1/2}}} hr
:
let d = the distance he has to walk
:
Write a time equation; time = dist/speed
{{{d/3}}} - {{{d/4}}} = {{{1/2}}}
multiply the equation by 12, cancel the denominators and you have
4d - 3d = 6
d = 6 km is the distance he walked</PRE>